As anyone who has walked into a smoky bar can tell you, alcohol and smoking often go hand in hand. Now two studies published in the journal Alcoholism: Clinical and Experimental Research suggest that they may in fact share similar mechanistic pathways in the brain. The findings could lead to a single treatment capable of benefiting both smokers and drinkers.

Yousef Tizabi of Howard University College of Medicine and colleagues gave rats both alcohol and nicotine. They analyzed the drugs' effects on the release of dopamine, a neurotransmitter that evokes feelings of pleasure and reward, in a region of the brain known as the nucleus accumbens. Although both drugs caused increases in dopamine release directly proportional to the administered dose, the researchers found that lower doses of the two substances administered simultaneously resulted in an additive effect on the release of dopamine that was not recorded with higher doses. The findings, Tazabi notes, "suggest that part of the reason why people drink and smoke at the same time is to increase their pleasure." He makes such interpretations cautiously, however, because the animals received the drugs only once. The effects in humans may be different--especially for those who smoke or drink habitually.

A second report in the same issue found that a nicotine-blocking compound also reduces the rewarding effects of alcohol in people. Mecamylamine has been used experimentally with the patch treatment for smoking cessation. Henry R. Kranzler of the University of Connecticut School of Medicine and colleagues tested the chemical's effect on 20 volunteers who took it before consuming a standard dose of alcohol. The subjects had their breath alcohol levels (BALs), blood pressure and heart rates measured and they filled out three questionnaires describing their reactions to the drinks. According to the study, mecamylamine reduced both BAL and the rewarding effects of alcohol. The researchers report that mecamylamine reduces the release of dopamine by blocking binding sites on so-called nicotinic cholinergic synapses. David Overstreet of the Bowles Center for Alcohol Studies at the University of North Carolina at Chapel Hill proposes that the results "raise the possibility that treatments that are effective in smoking cessation may also be beneficial for alcoholics."